Optical transmission impairments can be mitigated by using optical amplifier sites throughout an optical network, thereby achieving substantial optical performance enhancement, enabling longer system reach and higher network capacity. Accumulated loss and spectral ripple across wavelength channels can be compensated through a combination of optical amplifiers and optical filters, while accumulated dispersion can be compensated through periodically inserted dispersion compensation (DCM) units. For an optimized optical network transmission strategy, optimum optical signal to noise ratio (OSNR) is achieved by controlling the spectral power profile across wavelength channels launched into the optical fiber.
Although optical amplifier sites are complex network elements comprised of various optical devices, such as optical amplifiers, gain equalization filters, and DCM units, they do not typically employ dynamically adjustable optical devices. However, recently developed dynamic amplifier sites are beginning to incorporate dynamically adjustable optical devices.
Therefore, it is desirable to provide an improved optical control scheme for such dynamic optical amplifier sites. It is envisioned that the improved optical control scheme will enable steady state optimized optical network performance through a layered control strategy, distributed across multiple optical devices at the dynamic optical amplifier site. Distributed partitioning of the control objectives across individual optical devices will ensure optimized, flexible performance of the dynamic amplifier site. Functionally, optimization of the optical power spectrum shape launched from a dynamic amplifier site will be achieved via two levels of control: average power control achieved by variation of amplifier gain via pump laser control, and spectral power control to compensate for the spectral tilt and ripple via dynamic gain equalization and Raman control. This will enable compensation of the spectral tilt and ripple accumulated from a previous dynamic amplifier site, as well as compensation of slow varying perturbations like those due to polarization dependent loss (PDL) effects accumulated from various optical devices.